In the markets, many conventional printers (e.g. label printers) use paper rolls as print media. The label printer usually has a paper roll fixing device for fixing the paper roll within the label printer. After the paper roll is fixed within the label printer, the task of printing the label paper can be performed by the printing mechanism of the label printer.
FIG. 1A is a schematic perspective view illustrating a label printer according to the prior art. The label printer 1 is disclosed in U.S. Pat. No. 6,431,492. As shown in FIG. 1A, a paper roll fixing device 11 is installed within the label printer 1. The paper roll fixing device 11 comprises a first supporting base 12 and a second supporting base 13. Please refer to FIG. 1B and FIG. 1C. FIG. 1B schematically illustrates the first supporting base 12, a first movable track 14 and a second movable track 15 of the paper roll fixing device 11. FIG. 1C schematically illustrates the second supporting base 13, the first movable track 14, the second movable track 15 and the gear 16 of the paper roll fixing device 11. The first supporting base 12 comprises a supporting protrusion part 12a. The second supporting base 13 comprises a supporting protrusion part 13a. The paper roll fixing device 11 further comprises the first movable track 14, the second movable track 15 and the gear 16. The first movable track 14 and the second movable track 15 are parallel with each other. An end 14a of the first movable track 14 is connected with the first supporting base 12. An end 15a of the second movable track 15 is connected with the second supporting base 13. The gear 16 is clamped between the first movable track 14 and the second movable track 15, and engaged with the first movable track 14 and the second movable track 15. Through the gear 16, the first movable track 14 and the second movable track 15 may be linearly moved back and forth in a reciprocating manner. In such way, the distance between the first supporting base 12 and the second supporting base 13 is adjustable.
For installing a paper roll within the label printer 1, a first end of the paper roll is firstly fixed on the first supporting base 12. That is, the first end of the paper roll is fixed by the supporting protrusion part 12a. Then, the second supporting base 13 is moved toward the first supporting base 12. During the process of moving the second supporting base 13, the second movable track 15 that is connected with the second supporting base 13 and the first movable track 14 that is connected with the first supporting base 12 are linearly moved through the gear 16. As a consequence, the first supporting base 12 and the second supporting base 13 approach each other. Until the second end of the paper roll is fixed by the supporting protrusion part 13a of the second supporting base 13, the paper roll is fixed within the paper roll.
For removing the paper roller from the internal portion of the label printer 1, the first supporting base 12 or the second supporting base 13 needs to be pulled out. During the process of pulling out the first supporting base 12 or the second supporting base 13, the first movable track 14 and the second movable track 15 are moved relative to each other through the gear 16. As a consequence, the first supporting base 12 and the second supporting base 13 are distant from each other. Meanwhile, the both ends of the paper roll are no longer securely fixed by the supporting protrusion part 12a of the first supporting base 12 and the supporting protrusion part 13a of the second supporting base 13, and thus the paper roll may be removed without difficulty.
From the above discussion, the paper roll can be fixed within the internal portion of the label printer 1 by the first supporting base 12 and the second supporting base 13 of the paper roll fixing device 11.
However, the paper roll fixing device 11 of the label printer 1 still has some drawbacks. For introducing the paper roll into the internal portion of the label printer 1, a first end of the paper roll is firstly held by one hand of the user and fixed on the first supporting base 12, and then the distance between the first supporting base 12 and the second supporting base 13 is adjusted by the other hand of the user until the second end of the paper roll is fixed on the second supporting base 13. Whereas, for removing the paper roll, the distance between the first supporting base 12 and the second supporting base 13 is adjusted; and until the both ends of the paper roll are no longer fixed on the first supporting base 12 and the second supporting base 13, the paper roll is removed. In other way, since two hands or at least two steps are necessary to introduce the paper roll into the paper roll fixing device or remove the paper roll from the paper roll fixing device, the operations of the paper roll fixing device are inconvenient to the user.
Therefore, there is a need of providing an improved paper roll fixing device of a printer so as to obviate the drawbacks encountered from the prior art.